The present invention relates to a switching power amplifier and a method for controlling the switching power amplifier, and more particularly to a high efficiency digital power amplifying device, and the related controlling method.
In wireless communication system, such as the third generation (3G) mobile communication system, a high dynamic range of power is required. For example, a cellular may be required to output power with dynamic range of 78 dB. Normally, an on-chip transmitter capable of generating power range from 0 dBm to −78 dBm may comprise various components, such as digital-to-analog converter (DAC), low pass filter, programmable gain amplifier, modulator, and pre-driver, and those components are complicated and may occupy a large area of the transmitter. Therefore, replacing the transmitter by an RF power DAC, such as a digital transmitter using switch-mode power amplifier, may relax the hardware complexity. However, the digital transmitter may suffer from the problem of leakage power. More specifically, a switch-mode power amplifier may comprise a plurality of power amplifier cells, and each is arranged to amplify one bit among a plurality of inputting bits. If a first power amplifier cell is outputting a high voltage signal and a second power amplifier cell is outputting a low voltage signal, then a leakage current may be induced to flow to the second power amplifier cell from the first power amplifier cell. This phenomenon may cause a power loss to the switch-mode power amplifier. Therefore, how to avoid the power loss of a switch-mode power amplifier is an urgent problem in the wireless communication system.